1Photo credit: NASA2 You already know that the moon's gravity pulls on Earth's oceans and causes tides. But the moon affects Earth in other ways, too. Here are a few things you may not know about our moon.3 Many scientists believe that some object the size of the planet Mars hit Earth. It may have been a comet or an asteroid, but whatever it was, it knocked a huge chunk of Earth into space. This chunk became our moon. The collision caused Earth to tilt sideways slightly on its axis, giving us our seasons of spring, summer, fall, and winter.